-use rustc_data_structures::fx::FxHashMap;
-use syntax_pos::Span;
-
-use crate::hir::def_id::DefId;
use crate::hir;
+use crate::hir::def_id::DefId;
use crate::hir::Node;
-use crate::infer::{self, InferCtxt, InferOk, TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::outlives::free_region_map::FreeRegionRelations;
+use crate::infer::{self, InferCtxt, InferOk, TypeVariableOrigin, TypeVariableOriginKind};
+use crate::middle::region;
use crate::traits::{self, PredicateObligation};
-use crate::ty::{self, Ty, TyCtxt, GenericParamDefKind};
use crate::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder, TypeVisitor};
-use crate::ty::subst::{Kind, InternalSubsts, SubstsRef, UnpackedKind};
+use crate::ty::subst::{InternalSubsts, Kind, SubstsRef, UnpackedKind};
+use crate::ty::{self, GenericParamDefKind, Ty, TyCtxt};
use crate::util::nodemap::DefIdMap;
+use errors::DiagnosticBuilder;
+use rustc::session::config::nightly_options;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync::Lrc;
+use syntax_pos::Span;
pub type OpaqueTypeMap<'tcx> = DefIdMap<OpaqueTypeDecl<'tcx>>;
/// then `substs` would be `['a, T]`.
pub substs: SubstsRef<'tcx>,
+ /// The span of this particular definition of the opaque type. So
+ /// for example:
+ ///
+ /// ```
+ /// existential type Foo;
+ /// fn bar() -> Foo {
+ /// ^^^ This is the span we are looking for!
+ /// ```
+ ///
+ /// In cases where the fn returns `(impl Trait, impl Trait)` or
+ /// other such combinations, the result is currently
+ /// over-approximated, but better than nothing.
+ pub definition_span: Span,
+
/// The type variable that represents the value of the abstract type
/// that we require. In other words, after we compile this function,
/// we will be created a constraint like:
/// - `param_env` -- the in-scope parameter environment to be used for
/// obligations
/// - `value` -- the value within which we are instantiating opaque types
+ /// - `value_span` -- the span where the value came from, used in error reporting
pub fn instantiate_opaque_types<T: TypeFoldable<'tcx>>(
&self,
parent_def_id: DefId,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
value: &T,
+ value_span: Span,
) -> InferOk<'tcx, (T, OpaqueTypeMap<'tcx>)> {
- debug!("instantiate_opaque_types(value={:?}, parent_def_id={:?}, body_id={:?}, \
- param_env={:?})",
- value, parent_def_id, body_id, param_env,
+ debug!(
+ "instantiate_opaque_types(value={:?}, parent_def_id={:?}, body_id={:?}, \
+ param_env={:?})",
+ value, parent_def_id, body_id, param_env,
);
let mut instantiator = Instantiator {
infcx: self,
parent_def_id,
body_id,
param_env,
+ value_span,
opaque_types: Default::default(),
obligations: vec![],
};
let value = instantiator.instantiate_opaque_types_in_map(value);
- InferOk {
- value: (value, instantiator.opaque_types),
- obligations: instantiator.obligations,
- }
+ InferOk { value: (value, instantiator.opaque_types), obligations: instantiator.obligations }
}
/// Given the map `opaque_types` containing the existential `impl
///
/// # The Solution
///
- /// We make use of the constraint that we *do* have in the `<=`
- /// relation. To do that, we find the "minimum" of all the
- /// arguments that appear in the substs: that is, some region
- /// which is less than all the others. In the case of `Foo1<'a>`,
- /// that would be `'a` (it's the only choice, after all). Then we
- /// apply that as a least bound to the variables (e.g., `'a <=
- /// '0`).
+ /// We generally prefer to make `<=` constraints, since they
+ /// integrate best into the region solver. To do that, we find the
+ /// "minimum" of all the arguments that appear in the substs: that
+ /// is, some region which is less than all the others. In the case
+ /// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
+ /// all). Then we apply that as a least bound to the variables
+ /// (e.g., `'a <= '0`).
///
/// In some cases, there is no minimum. Consider this example:
///
/// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
/// ```
///
- /// Here we would report an error, because `'a` and `'b` have no
- /// relation to one another.
+ /// Here we would report a more complex "in constraint", like `'r
+ /// in ['a, 'b, 'static]` (where `'r` is some regon appearing in
+ /// the hidden type).
+ ///
+ /// # Constrain regions, not the hidden concrete type
+ ///
+ /// Note that generating constraints on each region `Rc` is *not*
+ /// the same as generating an outlives constraint on `Tc` iself.
+ /// For example, if we had a function like this:
+ ///
+ /// ```rust
+ /// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
+ /// (x, y)
+ /// }
+ ///
+ /// // Equivalent to:
+ /// existential type FooReturn<'a, T>: Foo<'a>;
+ /// fn foo<'a, T>(..) -> FooReturn<'a, T> { .. }
+ /// ```
+ ///
+ /// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
+ /// is an inference variable). If we generated a constraint that
+ /// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
+ /// but this is not necessary, because the existential type we
+ /// create will be allowed to reference `T`. So we only generate a
+ /// constraint that `'0: 'a`.
///
/// # The `free_region_relations` parameter
///
}
}
+ /// See `constrain_opaque_types` for documentation.
pub fn constrain_opaque_type<FRR: FreeRegionRelations<'tcx>>(
&self,
def_id: DefId,
debug!("constrain_opaque_type: concrete_ty={:?}", concrete_ty);
- let abstract_type_generics = tcx.generics_of(def_id);
+ let opaque_type_generics = tcx.generics_of(def_id);
let span = tcx.def_span(def_id);
// If there are required region bounds, we can use them.
if opaque_defn.has_required_region_bounds {
let predicates_of = tcx.predicates_of(def_id);
- debug!(
- "constrain_opaque_type: predicates: {:#?}",
- predicates_of,
- );
+ debug!("constrain_opaque_type: predicates: {:#?}", predicates_of,);
let bounds = predicates_of.instantiate(tcx, opaque_defn.substs);
debug!("constrain_opaque_type: bounds={:#?}", bounds);
let opaque_type = tcx.mk_opaque(def_id, opaque_defn.substs);
- let required_region_bounds = tcx.required_region_bounds(
- opaque_type,
- bounds.predicates,
- );
+ let required_region_bounds = tcx.required_region_bounds(opaque_type, bounds.predicates);
debug_assert!(!required_region_bounds.is_empty());
- for region in required_region_bounds {
- concrete_ty.visit_with(&mut OpaqueTypeOutlivesVisitor {
- infcx: self,
- least_region: region,
- span,
+ for required_region in required_region_bounds {
+ concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+ tcx: self.tcx,
+ op: |r| self.sub_regions(infer::CallReturn(span), required_region, r),
});
}
return;
// `['a]` for the first impl trait and `'b` for the
// second.
let mut least_region = None;
- for param in &abstract_type_generics.params {
+ for param in &opaque_type_generics.params {
match param.kind {
GenericParamDefKind::Lifetime => {}
- _ => continue
+ _ => continue,
}
+
// Get the value supplied for this region from the substs.
let subst_arg = opaque_defn.substs.region_at(param.index as usize);
least_region = Some(subst_arg);
} else {
// There are two regions (`lr` and
- // `subst_arg`) which are not relatable. We can't
- // find a best choice.
- let context_name = match opaque_defn.origin {
- hir::ExistTyOrigin::ExistentialType => "existential type",
- hir::ExistTyOrigin::ReturnImplTrait => "impl Trait",
- hir::ExistTyOrigin::AsyncFn => "async fn",
- };
- let msg = format!("ambiguous lifetime bound in `{}`", context_name);
- let mut err = self.tcx
- .sess
- .struct_span_err(span, &msg);
-
- let lr_name = lr.to_string();
- let subst_arg_name = subst_arg.to_string();
- let label_owned;
- let label = match (&*lr_name, &*subst_arg_name) {
- ("'_", "'_") => "the elided lifetimes here do not outlive one another",
- _ => {
- label_owned = format!(
- "neither `{}` nor `{}` outlives the other",
- lr_name,
- subst_arg_name,
- );
- &label_owned
- }
- };
- err.span_label(span, label);
-
- if let hir::ExistTyOrigin::AsyncFn = opaque_defn.origin {
- err.note("multiple unrelated lifetimes are not allowed in \
- `async fn`.");
- err.note("if you're using argument-position elided lifetimes, consider \
- switching to a single named lifetime.");
- }
- err.emit();
-
- least_region = Some(self.tcx.mk_region(ty::ReEmpty));
- break;
+ // `subst_arg`) which are not relatable. We
+ // can't find a best choice. Therefore,
+ // instead of creating a single bound like
+ // `'r: 'a` (which is our preferred choice),
+ // we will create a "in bound" like `'r in
+ // ['a, 'b, 'c]`, where `'a..'c` are the
+ // regions that appear in the impl trait.
+ return self.generate_member_constraint(
+ concrete_ty,
+ opaque_type_generics,
+ opaque_defn,
+ def_id,
+ lr,
+ subst_arg,
+ );
}
}
}
let least_region = least_region.unwrap_or(tcx.lifetimes.re_static);
debug!("constrain_opaque_types: least_region={:?}", least_region);
- concrete_ty.visit_with(&mut OpaqueTypeOutlivesVisitor {
- infcx: self,
- least_region,
- span,
+ concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+ tcx: self.tcx,
+ op: |r| self.sub_regions(infer::CallReturn(span), least_region, r),
});
}
+ /// As a fallback, we sometimes generate an "in constraint". For
+ /// a case like `impl Foo<'a, 'b>`, where `'a` and `'b` cannot be
+ /// related, we would generate a constraint `'r in ['a, 'b,
+ /// 'static]` for each region `'r` that appears in the hidden type
+ /// (i.e., it must be equal to `'a`, `'b`, or `'static`).
+ ///
+ /// `conflict1` and `conflict2` are the two region bounds that we
+ /// detected which were unrelated. They are used for diagnostics.
+ fn generate_member_constraint(
+ &self,
+ concrete_ty: Ty<'tcx>,
+ opaque_type_generics: &ty::Generics,
+ opaque_defn: &OpaqueTypeDecl<'tcx>,
+ opaque_type_def_id: DefId,
+ conflict1: ty::Region<'tcx>,
+ conflict2: ty::Region<'tcx>,
+ ) {
+ // For now, enforce a feature gate outside of async functions.
+ if self.member_constraint_feature_gate(
+ opaque_defn,
+ opaque_type_def_id,
+ conflict1,
+ conflict2,
+ ) {
+ return;
+ }
+
+ // Create the set of choice regions: each region in the hidden
+ // type can be equal to any of the region parameters of the
+ // opaque type definition.
+ let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
+ opaque_type_generics
+ .params
+ .iter()
+ .filter(|param| match param.kind {
+ GenericParamDefKind::Lifetime => true,
+ GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => false,
+ })
+ .map(|param| opaque_defn.substs.region_at(param.index as usize))
+ .chain(std::iter::once(self.tcx.lifetimes.re_static))
+ .collect(),
+ );
+
+ concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+ tcx: self.tcx,
+ op: |r| self.member_constraint(
+ opaque_type_def_id,
+ opaque_defn.definition_span,
+ concrete_ty,
+ r,
+ &choice_regions,
+ ),
+ });
+ }
+
+ /// Member constraints are presently feature-gated except for
+ /// async-await. We expect to lift this once we've had a bit more
+ /// time.
+ fn member_constraint_feature_gate(
+ &self,
+ opaque_defn: &OpaqueTypeDecl<'tcx>,
+ opaque_type_def_id: DefId,
+ conflict1: ty::Region<'tcx>,
+ conflict2: ty::Region<'tcx>,
+ ) -> bool {
+ // If we have `#![feature(member_constraints)]`, no problems.
+ if self.tcx.features().member_constraints {
+ return false;
+ }
+
+ let span = self.tcx.def_span(opaque_type_def_id);
+
+ // Otherwise, we allow for async-await but not otherwise.
+ let context_name = match opaque_defn.origin {
+ hir::ExistTyOrigin::ExistentialType => "existential type",
+ hir::ExistTyOrigin::ReturnImplTrait => "impl Trait",
+ hir::ExistTyOrigin::AsyncFn => {
+ // we permit
+ return false;
+ }
+ };
+ let msg = format!("ambiguous lifetime bound in `{}`", context_name);
+ let mut err = self.tcx.sess.struct_span_err(span, &msg);
+
+ let conflict1_name = conflict1.to_string();
+ let conflict2_name = conflict2.to_string();
+ let label_owned;
+ let label = match (&*conflict1_name, &*conflict2_name) {
+ ("'_", "'_") => "the elided lifetimes here do not outlive one another",
+ _ => {
+ label_owned = format!(
+ "neither `{}` nor `{}` outlives the other",
+ conflict1_name, conflict2_name,
+ );
+ &label_owned
+ }
+ };
+ err.span_label(span, label);
+
+ if nightly_options::is_nightly_build() {
+ help!(err,
+ "add #![feature(member_constraints)] to the crate attributes \
+ to enable");
+ }
+
+ err.emit();
+ true
+ }
+
/// Given the fully resolved, instantiated type for an opaque
/// type, i.e., the value of an inference variable like C1 or C2
/// (*), computes the "definition type" for an abstract type
// Convert the type from the function into a type valid outside
// the function, by replacing invalid regions with 'static,
// after producing an error for each of them.
- let definition_ty =
- instantiated_ty.fold_with(&mut ReverseMapper::new(
- self.tcx,
- self.is_tainted_by_errors(),
- def_id,
- map,
- instantiated_ty,
- ));
- debug!(
- "infer_opaque_definition_from_instantiation: definition_ty={:?}",
- definition_ty
- );
+ let definition_ty = instantiated_ty.fold_with(&mut ReverseMapper::new(
+ self.tcx,
+ self.is_tainted_by_errors(),
+ def_id,
+ map,
+ instantiated_ty,
+ ));
+ debug!("infer_opaque_definition_from_instantiation: definition_ty={:?}", definition_ty);
definition_ty
}
}
+pub fn unexpected_hidden_region_diagnostic(
+ tcx: TyCtxt<'tcx>,
+ region_scope_tree: Option<®ion::ScopeTree>,
+ opaque_type_def_id: DefId,
+ hidden_ty: Ty<'tcx>,
+ hidden_region: ty::Region<'tcx>,
+) -> DiagnosticBuilder<'tcx> {
+ let span = tcx.def_span(opaque_type_def_id);
+ let mut err = struct_span_err!(
+ tcx.sess,
+ span,
+ E0700,
+ "hidden type for `impl Trait` captures lifetime that does not appear in bounds",
+ );
+
+ // Explain the region we are capturing.
+ if let ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic | ty::ReEmpty = hidden_region {
+ // Assuming regionck succeeded (*), we ought to always be
+ // capturing *some* region from the fn header, and hence it
+ // ought to be free. So under normal circumstances, we will go
+ // down this path which gives a decent human readable
+ // explanation.
+ //
+ // (*) if not, the `tainted_by_errors` flag would be set to
+ // true in any case, so we wouldn't be here at all.
+ tcx.note_and_explain_free_region(
+ &mut err,
+ &format!("hidden type `{}` captures ", hidden_ty),
+ hidden_region,
+ "",
+ );
+ } else {
+ // Ugh. This is a painful case: the hidden region is not one
+ // that we can easily summarize or explain. This can happens
+ // in a case like
+ // `src/test/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
+ //
+ // ```
+ // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
+ // if condition() { a } else { b }
+ // }
+ // ```
+ //
+ // Here the captured lifetime is the intersection of `'a` and
+ // `'b`, which we can't quite express.
+
+ if let Some(region_scope_tree) = region_scope_tree {
+ // If the `region_scope_tree` is available, this is being
+ // invoked from the "region inferencer error". We can at
+ // least report a really cryptic error for now.
+ tcx.note_and_explain_region(
+ region_scope_tree,
+ &mut err,
+ &format!("hidden type `{}` captures ", hidden_ty),
+ hidden_region,
+ "",
+ );
+ } else {
+ // If the `region_scope_tree` is *unavailable*, this is
+ // being invoked by the code that comes *after* region
+ // inferencing. This is a bug, as the region inferencer
+ // ought to have noticed the failed constraint and invoked
+ // error reporting, which in turn should have prevented us
+ // from getting trying to infer the hidden type
+ // completely.
+ span_bug!(
+ span,
+ "hidden type captures unexpected lifetime `{:?}` but no region inference failure",
+ hidden_region,
+ );
+ }
+ }
+
+ err
+}
+
// Visitor that requires that (almost) all regions in the type visited outlive
// `least_region`. We cannot use `push_outlives_components` because regions in
// closure signatures are not included in their outlives components. We need to
//
// We ignore any type parameters because impl trait values are assumed to
// capture all the in-scope type parameters.
-struct OpaqueTypeOutlivesVisitor<'a, 'tcx> {
- infcx: &'a InferCtxt<'a, 'tcx>,
- least_region: ty::Region<'tcx>,
- span: Span,
+struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
+where
+ OP: FnMut(ty::Region<'tcx>),
+{
+ tcx: TyCtxt<'tcx>,
+ op: OP,
}
-impl<'tcx> TypeVisitor<'tcx> for OpaqueTypeOutlivesVisitor<'_, 'tcx> {
+impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
+where
+ OP: FnMut(ty::Region<'tcx>),
+{
fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &ty::Binder<T>) -> bool {
t.skip_binder().visit_with(self);
false // keep visiting
// ignore bound regions, keep visiting
ty::ReLateBound(_, _) => false,
_ => {
- self.infcx.sub_regions(infer::CallReturn(self.span), self.least_region, r);
+ (self.op)(r);
false
}
}
ty::Closure(def_id, ref substs) => {
// Skip lifetime parameters of the enclosing item(s)
- for upvar_ty in substs.upvar_tys(def_id, self.infcx.tcx) {
+ for upvar_ty in substs.upvar_tys(def_id, self.tcx) {
upvar_ty.visit_with(self);
}
- substs.closure_sig_ty(def_id, self.infcx.tcx).visit_with(self);
+ substs.closure_sig_ty(def_id, self.tcx).visit_with(self);
}
ty::Generator(def_id, ref substs, _) => {
// Skip lifetime parameters of the enclosing item(s)
// Also skip the witness type, because that has no free regions.
- for upvar_ty in substs.upvar_tys(def_id, self.infcx.tcx) {
+ for upvar_ty in substs.upvar_tys(def_id, self.tcx) {
upvar_ty.visit_with(self);
}
- substs.return_ty(def_id, self.infcx.tcx).visit_with(self);
- substs.yield_ty(def_id, self.infcx.tcx).visit_with(self);
+ substs.return_ty(def_id, self.tcx).visit_with(self);
+ substs.yield_ty(def_id, self.tcx).visit_with(self);
}
_ => {
ty.super_visit_with(self);
None => {
if !self.map_missing_regions_to_empty && !self.tainted_by_errors {
if let Some(hidden_ty) = self.hidden_ty.take() {
- let span = self.tcx.def_span(self.opaque_type_def_id);
- let mut err = struct_span_err!(
- self.tcx.sess,
- span,
- E0700,
- "hidden type for `impl Trait` captures lifetime that \
- does not appear in bounds",
- );
-
- // Assuming regionck succeeded, then we must
- // be capturing *some* region from the fn
- // header, and hence it must be free, so it's
- // ok to invoke this fn (which doesn't accept
- // all regions, and would ICE if an
- // inappropriate region is given). We check
- // `is_tainted_by_errors` by errors above, so
- // we don't get in here unless regionck
- // succeeded. (Note also that if regionck
- // failed, then the regions we are attempting
- // to map here may well be giving errors
- // *because* the constraints were not
- // satisfiable.)
- self.tcx.note_and_explain_free_region(
- &mut err,
- &format!("hidden type `{}` captures ", hidden_ty),
+ unexpected_hidden_region_diagnostic(
+ self.tcx,
+ None,
+ self.opaque_type_def_id,
+ hidden_ty,
r,
- ""
- );
-
- err.emit();
+ ).emit();
}
}
self.tcx.lifetimes.re_empty
- },
+ }
}
}
// during codegen.
let generics = self.tcx.generics_of(def_id);
- let substs = self.tcx.mk_substs(substs.substs.iter().enumerate().map(
- |(index, &kind)| {
+ let substs =
+ self.tcx.mk_substs(substs.substs.iter().enumerate().map(|(index, &kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_mapping_missing_regions_to_empty(kind)
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
- },
- ));
+ }));
self.tcx.mk_closure(def_id, ty::ClosureSubsts { substs })
}
ty::Generator(def_id, substs, movability) => {
let generics = self.tcx.generics_of(def_id);
- let substs = self.tcx.mk_substs(substs.substs.iter().enumerate().map(
- |(index, &kind)| {
+ let substs =
+ self.tcx.mk_substs(substs.substs.iter().enumerate().map(|(index, &kind)| {
if index < generics.parent_count {
// Accommodate missing regions in the parent kinds...
self.fold_kind_mapping_missing_regions_to_empty(kind)
// ...but not elsewhere.
self.fold_kind_normally(kind)
}
- },
- ));
+ }));
self.tcx.mk_generator(def_id, ty::GeneratorSubsts { substs }, movability)
}
parent_def_id: DefId,
body_id: hir::HirId,
param_env: ty::ParamEnv<'tcx>,
+ value_span: Span,
opaque_types: OpaqueTypeMap<'tcx>,
obligations: Vec<PredicateObligation<'tcx>>,
}
let parent_def_id = self.parent_def_id;
let def_scope_default = || {
let opaque_parent_hir_id = tcx.hir().get_parent_item(opaque_hir_id);
- parent_def_id == tcx.hir()
- .local_def_id_from_hir_id(opaque_parent_hir_id)
+ parent_def_id
+ == tcx.hir().local_def_id_from_hir_id(opaque_parent_hir_id)
};
- let (in_definition_scope, origin) =
- match tcx.hir().find(opaque_hir_id)
- {
+ let (in_definition_scope, origin) = match tcx.hir().find(opaque_hir_id) {
Some(Node::Item(item)) => match item.node {
// Anonymous `impl Trait`
hir::ItemKind::Existential(hir::ExistTy {
let infcx = self.infcx;
let tcx = infcx.tcx;
- debug!(
- "instantiate_opaque_types: Opaque(def_id={:?}, substs={:?})",
- def_id, substs
- );
+ debug!("instantiate_opaque_types: Opaque(def_id={:?}, substs={:?})", def_id, substs);
// Use the same type variable if the exact same opaque type appears more
// than once in the return type (e.g., if it's passed to a type alias).
return opaque_defn.concrete_ty;
}
let span = tcx.def_span(def_id);
- let ty_var = infcx.next_ty_var(TypeVariableOrigin {
- kind: TypeVariableOriginKind::TypeInference,
- span,
- });
+ let ty_var = infcx
+ .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
let predicates_of = tcx.predicates_of(def_id);
- debug!(
- "instantiate_opaque_types: predicates={:#?}",
- predicates_of,
- );
+ debug!("instantiate_opaque_types: predicates={:#?}", predicates_of,);
let bounds = predicates_of.instantiate(tcx, substs);
debug!("instantiate_opaque_types: bounds={:?}", bounds);
let required_region_bounds = tcx.required_region_bounds(ty, bounds.predicates.clone());
- debug!(
- "instantiate_opaque_types: required_region_bounds={:?}",
- required_region_bounds
- );
+ debug!("instantiate_opaque_types: required_region_bounds={:?}", required_region_bounds);
// Make sure that we are in fact defining the *entire* type
// (e.g., `existential type Foo<T: Bound>: Bar;` needs to be
// defined by a function like `fn foo<T: Bound>() -> Foo<T>`).
- debug!(
- "instantiate_opaque_types: param_env={:#?}",
- self.param_env,
- );
- debug!(
- "instantiate_opaque_types: generics={:#?}",
- tcx.generics_of(def_id),
- );
+ debug!("instantiate_opaque_types: param_env={:#?}", self.param_env,);
+ debug!("instantiate_opaque_types: generics={:#?}", tcx.generics_of(def_id),);
+
+ // Ideally, we'd get the span where *this specific `ty` came
+ // from*, but right now we just use the span from the overall
+ // value being folded. In simple cases like `-> impl Foo`,
+ // these are the same span, but not in cases like `-> (impl
+ // Foo, impl Bar)`.
+ let definition_span = self.value_span;
self.opaque_types.insert(
def_id,
OpaqueTypeDecl {
substs,
+ definition_span,
concrete_ty: ty_var,
has_required_region_bounds: !required_region_bounds.is_empty(),
origin,
// Require that the predicate holds for the concrete type.
debug!("instantiate_opaque_types: predicate={:?}", predicate);
- self.obligations
- .push(traits::Obligation::new(cause, self.param_env, predicate));
+ self.obligations.push(traits::Obligation::new(cause, self.param_env, predicate));
}
ty_var
);
// Named existential types can be defined by any siblings or children of siblings.
- let scope = tcx.hir()
- .get_defining_scope(opaque_hir_id)
- .expect("could not get defining scope");
+ let scope = tcx.hir().get_defining_scope(opaque_hir_id).expect("could not get defining scope");
// We walk up the node tree until we hit the root or the scope of the opaque type.
while hir_id != scope && hir_id != hir::CRATE_HIR_ID {
hir_id = tcx.hir().get_parent_item(hir_id);
projects / rust.git / blobdiff